1. Field of the Invention
The present invention relates to portable wireless apparatuses and, more particularly, to antenna devices with similar antenna characteristics in different directions.
2. Description of the Related Art
Among antenna devices for use with wireless apparatuses antenna devices using two conductive plates placed substantially parallel to each other are known. In one example, disclosed in Japanese Laid-Open Patent Application No. 1-241927, two conductive plates are spaced from each other so as to define a gap between them, and the conductive plates are short-circuited by a short-circuit portion. A capacitance element is loaded at a feed point in order to form a loop antenna as shown in the circuit diagram. In another example, as disclosed in Japanese Laid-Open Patent Application No. 6-244618, a loop antenna is shown in which short-circuit conductors for short-circuiting the feed point and the two conductive plates are placed at nearly diagonal positions.
However, when such antenna devices are used with a portable wireless apparatus using a conventional loop antenna, the antenna dimensions must be small because of the portable feature desired, and it is difficult to obtain the necessary or sufficient antenna gain. Thus, it is difficult to maintain satisfactory sensitivity of the wireless apparatus.